Cryopreservation of apple using non-desiccated sections from winter-collected scions.

Winter vegetative buds of Malus species are cryopreserved at USDA-ARS NCGRP to backup genetic resources maintained by field collections. The method uses desiccation of nodal sections prior to cooling but is time and labor intensive, and can damage materials if excessive. Here we tested cooling sections without prior desiccation to improve the efficiency of handling. Sections were slowly cooled to -30 degrees C or -35 degrees C and transferred to the vapor phase over liquid nitrogen (LNV). Viability was assessed using a sprouting test or grafting test. Some accessions showed higher viability when cooled at 5 degrees C/day compared to 1 degrees C/h and when transferred to LNV at -35 degrees C compared to -30 degrees C. Ten of 20 species had accessions that were successfully cryopreserved using a criterion of 50% or greater sprouting. Desiccation prior to cooling was not necessary for cryopreservation of winter-collected scions from these Malus species.